The Ministry of Health is tightening the safety guidelines for drugs taken by thousands of children to control hyperactivity, because of growing concerns over links to heart, brain and psychiatric disorders.

Ritalin and copies of it, whose active ingredient is methylphenidate, are used mainly to treat children and adolescents with the behavioural problem known as attention deficit hyperactivity disorder (ADHD). These drugs were prescribed to more than 5000 patients last year.

The ministry's Medsafe unit yesterday advised all doctors and other medicine prescribers that the approved uses of methylphenidate will shortly be changed in line with changes in Europe to specifically not use any version of the drug in people with:

*Circulatory disorders of the heart or brain,

or

*Any of a range of psychiatric disorders, including anorexia, psychotic symptoms and severe depression.

These matters are discussed in the current data sheets, which lay out the approved uses, but they come under the heading of special warnings and precautions. In the updated data sheets, they will be upgraded into the section headed "contra-indications" - do not prescribe - where they will join anxiety, agitation, cardiac arrhythmia, severe angina and several other conditions.

Another change is that patients prescribed methylphenidate should have their blood pressure checked at least every six months.

"Methylphenidate can cause or worsen some psychiatric disorders such as depression, suicidal thoughts, hostility, anxiety, agitation, psychosis and mania. Psychiatric well-being should therefore be monitored in patients treated with methylphenidate," Medsafe said in its publication Prescriber Update.

"It is also important to remember that the long-term effects of methylphenidate treatment in children are not fully understood. For patients who require long-term treatment - more than 12 months - the data sheets will recommend that a treatment holiday occur at least once a year. A treatment holiday will help determine whether methylphenidate treatment needs to be continued."

Child and adolescent psychiatrists said yesterday the changes were broadly in line with current practice but questioned the value of six-monthly blood pressure checks.

Emeritus Professor John Werry said methylphenidate was not prescribed to people with psychiatric disorders because it was known stimulant drugs could make conditions worse.

College of Psychiatrists spokesman Dr Arran Culver said the ministry guideline was to review patients annually. He was not aware of any evidence showing six-monthly blood-pressure checks would confer any benefit.

He said there was only limited evidence that drug holidays - occasionally withdrawing the drug - were beneficial.

"Parents should be given the choice about a medication holiday. Many families can do that and are happy to; some families would struggle to implement it because going off the medication will cause a significant deterioration in overall behaviour."